Search NASA⌕ Search

SEARCH · Search NASA

Results for “lattice parameters”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Shear strength of a refractory high entropy alloy MoNbTaVW under high pressure

Radial X-ray diffraction (R-XRD) was performed in situ using a Panoramic Diamond Anvil Cell on the refractory high entropy alloy MoNbTaVW. The lattice parameters were determined through a Le Bail fit using a body centered cubic (BCC) lattice of symmetry $Im$$\overline{3}$$m$ (international space group number 229). Upper and lower bounds to the shear strength were determined up to 80 GPa nonhydrostatically using copper as a pressure standard. The equation of state was derived at the magic angle ψ = 54.7° and yielded a bulk modulus of K 0 = 220.8 ± 1.65 GPa. The experimental lattice parameters and bulk modulus match closely with corresponding density functional theory (DFT) calculations. The BCC phase remains stable up to the highest pressure of 80 GPa studied and is shown to be elastically anisotropic. The shear strength was found to saturate around 70 GPa with a value of τ = 1.75 GPa, and the shear moduli are presented in different limits of iso-strain and iso-stress.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Low-temperature magnetic structure and lattice response in SmCuAs 2

We investigated the structural and magnetic properties of single-crystalline SmCuAs 2 using high-resolution synchrotron x-ray diffraction and x-ray resonant magnetic scattering (XRMS) at the Sm 𝐿 2 and 𝐿 3 edges. Temperature-dependent diffraction measurements confirm that SmCuAs2 maintains its tetragonal symmetry from room temperature down to 8 K, with lattice parameters showing anomalous behavior below the resistivity minimum (𝑇≈30K). Notably, the c-axis lattice parameter exhibits a plateau and subsequent increase near the Néel temperature, indicating magnetoelastic coupling. XRMS measurements reveal a commensurate antiferromagnetic structure with a propagation vector 𝒒=(0,0,0.5). Our measurement shows that the Sm moments are aligned within the 𝒂𝒃 plane and arranged in a ++−− stacking along the 𝒄 axis. Comparison with related 𝑅⁢𝐸⁢CuAs 2 compounds (RE = Pr, Nd, and Gd) suggests that in-plane moment orientation and associated magnetic frustration play a key role in the emergence of the resistivity minimum. Differences in spin-orbit and magnetoelastic coupling across the series highlight their importance in governing low-temperature transport behavior.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Synthesis and Thermal Oxidation Resistance of Boron-Rich Boron–Carbide Material

A boron-rich boron–carbide material (B4+δC) was synthesized by spark plasma sintering of a ball-milled mixture of high-purity boron powder and graphitic carbon at a pressure of 7 MPa and a temperature of 1930 °C. This high-pressure, high-temperature synthesized material was recovered and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, Vickers hardness measurements, and thermal oxidation studies. The X-ray diffraction studies revealed a single-phase rhombohedral structure (space group R-3m) with lattice parameters in hexagonal representation as a = 5.609 ± 0.007 Å and c = 12.082 ± 0.02 Å. The experimental lattice parameters result in a value of δ = 0.55, or the composition of the synthesized compound as B4.55C. The high-resolution scans of boron binding energy reveal the existence of a B-C bond at 188.5 eV. Raman spectroscopy reveals the existence of a 386 cm−1 vibrational mode representative of C-B-B linear chain formation due to excess boron in the lattice. The measured Vickers microhardness at a load of 200 gf shows a high hardness value of 33.8 ± 2.3 GPa. Thermal gravimetric studies on B4.55C were conducted at a temperature of 1300 °C in a compressed dry air environment, and its behavior is compared to other high-temperature ceramic materials such as high-entropy transition metal boride. The high neutron absorption cross section, high melting point, high mechanical strength, and thermal oxidation resistance make this material ideal for applications in extreme environments.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Disorder-induced magnetoelastic behaviors of MnTexSbyBi1-x-y alloys

This dataset contains input and output files from density functional theory (DFT) simulations used to study the disorder-induced magnetoelastic behaviors of MnTexSbyBi1-x-y (0 ≤ x + y ≤ 1) alloys and their binary end members MnTe, MnSb, and MnBi. The alloys adopt the hexagonal NiAs-type (nickeline) structure and span ternary (MnTexSb1-x, MnTexBi1-x, MnBixSb1-x), and quaternary compositions across the full MnTe–MnSb–MnBi composition triangle. For each alloy composition, the dataset provides DFT calculations in three magnetic configurations: A-type antiferromagnetic (AFM), C-type AFM, and ferromagnetic (FM). Every magnetic configuration folder contains the fully relaxed crystal structure (CONTCAR), VASP input parameters (INCAR), and the main VASP output file (OUTCAR), from which total electronic energies, Mn magnetic moments, lattice parameters, and percent volume changes between magnetic states are extracted. These data are used to construct compositional phase diagrams, evaluate thermodynamic stability (formability), and map magnetoelastic responses across the alloy space. For A-type AFM and FM configurations, additional data are provided as follows: (i) FORCE_CONSTANTS and thermal_properties.yaml files at the top level of A-type_AFM/ and FM/ folders — present only for compositions marked with an asterisk (*) in Table I of the main text. These are derived from Phonopy finite-displacement calculations on full disordered 128-atom supercells and provide vibrational free energy, entropy (Svib)contribution from explicit disorder calculations. (Table I of the associated main manuscript) (ii) A VCA/ subfolder within A-type_AFM/ and FM/, containing FORCE_CONSTANTS and thermal_properties.yaml from Virtual Crystal Approximation phonon calculations (without spin-orbit coupling). VCA data are available for all compositions and are used to estimate vibrational contributions to the Gibbs free energy across the full composition space. (iii) A SOC/ subfolder containing CONTCAR, INCAR, and OUTCAR from spin-orbit coupling calculations, providing relativistic corrections to electronic energies and lattice parameters (Tables S2–S3 of the SM, and Table I of the main manuscript). (iv) A SOC/VCA/ subfolder containing FORCE_CONSTANTS and thermal_properties.yaml from VCA phonon calculations performed within the SOC framework, combining relativistic and vibrational thermodynamic corrections. The computed properties are used to map the AFM–FM magnetic crossover near MnTe0.75Sb0.25, demonstrate disorder- and spin-induced phonon broadening, identify a semiconductor-to-metal crossover, and quantify the pronounced magnetoelastic volume response near the magnetic phase boundary.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Performance and properties evolution of near-term accident tolerant fuel: Cr-doped UO 2

Chromium-doped UO 2 fuel has received significant interest due to the ability for chromium to produce pellets with large average grain size (>30 μm), which has shown to increase fission gas retention during operation. Sintering of chromium-doped UO 2 pellets was pursued with oxygen potential and sintering atmosphere controlled to tailor the final microstructure of the material. Chromium additions in this study ranged from 750 to 7800 ppm. Cr concentrations were studied pre and post sintering using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Effects of chromium content on lattice parameter and microstructure were examined with X-ray diffraction (XRD) and scanning electron microscopy (SEM). Contraction of the UO 2 lattice parameter was observed, as well as enlargement of grain size with increasing chromium content up to 4900 ppm Cr 2 O 3 . In addition, SEM indicated Cr incorporation within the matrix and the formation of chromium oxide precipitates throughout the microstructure at high Cr concentrations. Evaluation of thermophysical properties of Cr-doped UO 2 pellets were conducted up to 1200 °C to illustrate their evolution with increased dopant concentration and microstructural changes. The results show that grain size is maximized at 52 μm with Cr 2 O 3 concentration equal to 4900 ppm; however, grain size decreases at higher Cr 2 O 3 concentrations. No significant changes were observed in specific heat capacity, linear thermal expansion, and coefficient of thermal expansion compared to undoped UO 2 . The thermal conductivity also decreased through the incorporation of Cr 2 O 3 dopants above 750 ppm and is shown to be ~15 % lower than reported UO 2 values.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Reversible Oxidation Quantified by Optical Properties in Epitaxial Fe2CrO4+d Films on (001) MgAl2O4

We report on the structural and optical properties of Fe2CrO4+d epitaxial films grown by molecular beam epitaxy on MgAl2O4 (001) as a function of ?. The average Fe valence can be correlated with the out-of-plane lattice parameter and the extent of light absorption in the infrared spectral region. Over-oxidized films (0 < d < 0.5) exhibit reduced lattice parameters and suppressed infrared absorption. We discuss the behavior of a novel infrared transition at ~0.6 eV in stoichiometric Fe2CrO4 films deposited on MgAl2O4 (MAO) at or above 400 °C. This research provides new insight into the atomic structure, optical processes, oxidation states, electronic structure, and application potentials of Fe2CrO4+d.

ellipsometry, Epitaxy, thin film, oxidation, reduc↗
DOE OSTI2024

Effect of XC functionals and dispersion corrections on the DFT‐computed structural and vibrational properties of SrCl 2 –NaCl and ZrF 4 –LiF

Density functional theory (DFT) calculations were performed to examine the impact of exchange–correlation (XC) functionals and van der Waals corrections (specifically the D3 method) on the structural and vibrational properties of the SrCl 2 –NaCl and ZrF 4 –LiF salt systems. Multiple XC functionals, including the local density approximation (LDA), the generalized gradient approximation using the Perdew–Burke–Ernzerhof (PBE) model, and its modified form suitable for solids (PBEsol), the dispersion-corrected PBE-D3 and PBEsol-D3, were considered. Of these functionals, LDA was found to exhibit the highest degree of error, while PBEsol and PBE-D3 displayed the least error. Underestimated lattice parameters compared with experimental values were observed to result in higher force constants, leading to an overprediction of vibrational frequencies. Conversely, an overestimation of lattice parameters was associated with lower vibrational frequencies. The methodology presented in this study yielded results that are in good agreement with experiment, irrespective of the method (finite differences vs. density functional perturbation theory) employed for calculating infrared and Raman spectra. It was further demonstrated that for alkali halides with weak Raman scattering, utilizing a supercell constructed from primitive cells better predicts Raman features than does the use of conventional cells.

Raman↗
DOE OSTI2020

Tunable Magnetic Exchange between Rare-Earth Metal 5d and Iron 3d States: A Case Study of the Multiple Magnetic Transitions in Gd 6 FeBi 2 and the Solid Solutions Dy 6– x Gd x FeBi 2 (1 ≤ x ≤ 5) with Curie Temperatures in the Range 120–350 K

In this paper, the room-temperature magnet Gd 6 FeBi 2 was comprehensively characterized by means of temperature-dependent single-crystal X-ray diffraction, magnetization measurements, and experimental electron density and electronic structure computations. This work explores the electron-spin effects of Fe on this structure and suggests that Gd6FeBi2 shows structural features and exchange interactions, which are clearly distinguishable from other analogues, including the solid solutions Dy 6–x Gd x FeBi 2 (0 ≤ x ≤ 5). The unique traits of Gd 6 FeBi 2 and its derivatives encompass abnormal variations of lattice parameters with the temperature, as well as the presence of multiple magnetic transitions of complex nature. Based on the comprehensive analyses, it can be suggested that the unique magnetic response in this material is the result from tunable Fe spin states, which are coupled with strong Gd 5d–Fe 3d interactions, which differ from other members of this large, structural family. In the ground state, according to density functional theory calculations, the Fe atom carries two net electrons, whose spins are coupled in an antiparallel fashion to the spins of the Gd electrons. Near the Curie temperature, the Fe net moment is reduced intermittently, coupled with a multiple of magnetic transitions. The magnetic correlations are manifested in unexpected variations of the lattice parameters as a function of temperature, suggesting spin–lattice interactions. Furthermore, this study emphasizes the important role of Gd 5d electrons in tuning Fe 3d-based magnetic contribution, which enables better understanding on the spin coupling in other related compounds and sheds light on the development of new magnetic and spintronic compounds.

36 MATERIALS SCIENCE↗
DOE OSTI2024

High-temperature structure, elasticity, and thermal expansion of ε-ZrH 1.8

Zirconium hydride is a promising candidate material for nuclear microreactor applications as a solid-state moderator component, owing to its favorable neutronics properties and good thermal stability over other metal hydrides. Here, in the present work, the crystal structure, thermal expansion, and elastic properties of the hydrogen-rich ε phase hydride were measured at elevated temperatures in the range 300–900 K. Samples were prepared by direct hydriding Zircaloy-4 metal – a nuclear-grade zirconium alloy. Room-temperature lattice parameters agree well with those reported from literature for unalloyed zirconium hydride and fall within an observed quadratic H-content dependence. The coefficients of thermal expansion, determined from lattice expansion and dilatometry, agree well within our work but were about 30 % lower than those reported by others for unalloyed hydrides. Density functional theory-based molecular dynamics simulations were used to compare with thermal expansion and elasticity measurements. Results showed lattice parameter temperature dependence and slope of thermal expansion align with those from measurements. Based on diffraction scans at select temperatures, ε phase remained stable in air up to at least 770 K. Likewise, dilatometry showed smooth thermal expansion up to the thermal decomposition temperature around 950 K. The precise decomposition temperature was not determined via diffraction due to sparse scanning. The complete elastic property measurements were gathered for ε-phase Ziracloy-4 hydride for the first time. Young's modulus was lower compared to the metal and δ hydride phases. High-temperature elasticity measurements were limited to <350 K due to acoustic dissipation effects.

36 MATERIALS SCIENCE↗
DOE OSTI2026

High energy X-ray characterization of the microstructure of PuGa alloy samples at macroscopic depths and non-ambient conditions

High energy (95 keV) X-rays were utilized to characterize the microstructure of eight PuGa alloy samples at room temperature and during cooling to ∼10 K. The samples had different Ga content (nominally 0-3.4 at.%), age, and history. A ninth sample, similarly characterized with neutron diffraction, was included to extend the Ga range to 7 at.%. The samples span the range from single phase α (monoclinic) to δ (face-centered cubic) PuGa, as well as a two-phase α′/δ sample. The crystallographic textures, phase fractions, lattice parameters and dislocation densities of each sample were evaluated through distinct analysis techniques. The textures of the samples were modest. In each case, the dislocation densities were relatively high, comparable to cold worked metals and metals exposed to similar radiation dose. At room temperature, the lattice parameters determined in the predominantly single-phase samples were larger than expected based on the nominal Ga concentration. The observed lattice thermal expansions of the single-phase δ samples to 10 K are self-consistent across the samples and consistent with previous measurements reported in the literature. Significantly larger thermal lattice strain is observed in the δ phase of the two-phase material due to mechanical constraint from the α′ phase, which has a three times larger thermal expansion and is much harder than the δ phase. In conclusion, the results demonstrate the unique value of high-energy X-rays for relatively routine microstructural characterization of Pu alloy samples.

36 MATERIALS SCIENCE↗
DOE OSTI2021

The hydrogen-containing bronzes H 0.23 WO 3 and H 0.10 ReO 3 synthesized via a polymer route

We report the synthesis of two hydrogen-containing perovskite-type bronzes H 0.23 WO 3 and H 0.10 ReO 3 utilizing an unconventional solid-state synthetic approach, involving the use of the polymer Poly(vinylidene fluoride) (CH 2 CF 2 ) n. Powder neutron diffraction at ambient temperature shows that H 0.23 WO 3 crystallizes in a tetragonal symmetry distortion of the simple perovskite structure (space group P4/nmm), with lattice parameters a = 5.2279(2) Å, and c =3.8763(1) Å. H 0.10 ReO 3 , in contrast, crystallizes in a monoclinic distortion of a simple cubic perovskite (space group P2/m), with lattice parameters a = 5.3125(1) Å, b = 5.3155(3) Å, c = 3.7045(3) Å, and γ = 90.43(1)°. Both H 0.23 WO 3 and H 0.10 ReO 3 exhibit intrinsically diamagnetic behavior, with low temperature paramagnetic upturns and no signs of bulk superconductivity down to 0.35 K.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Assessment of diagenesis in archaeological human second metacarpal bones using the intensity of the small angle X-ray scattering D -period peak

Bone consists mainly of carbonated apatite (cAp) nanoplatelets embedded in a matrix of collagen fibrils. Earlier, high-energy small angle X-ray scattering (SAXS) studies of archaeological adult human second metacarpal bones (mc2) found collagen D-period peaks with high-intensity I D in specimens in which microcomputed tomography (microCT) showed little diagenesis and I D ~ 0 for specimens where microCT revealed severe diagenesis (Park et al. 2022 Int. J. Osteoarchaeol. 32, 170–181 (doi:10.1002/oa.3053); Stock et al. 2022 Int. J. Osteoarchaeol. 32, 120–131 (doi:10.1002/oa.3049)). Here, the present paper uses SAXS at beamline 1-ID, Advanced Photon Source, Argonne National Laboratory and other techniques to study a set of 10 mc2 from an early Medieval cemetery at Greding, Germany. We hypothesized that non-invasive measurement of I D would provide an accurate and rapid (approx. 6 min/specimen) assessment of diagenesis in archaeological mc2. Results of Raman spectroscopy, laboratory microCT and backscattered electron, reflected light and polarized transmitted light microscopies confirmed the SAXS determinations, but lattice parameter values from X-ray diffraction were uncorrelated with I D value. Age-at-death estimates placed the 10 mc2 in three age categories (young adult, middle adult, old adult): lattice parameters from X-ray diffraction were uncorrelated with age at death. Cross-sectional bone area fraction from microCT dropped noticeably for the older age cohort.

Raman spectroscopy↗
DOE OSTI2022

Fathoming the anisotropic magnetoelasticity and magnetocaloric effect in GdNi

Intermetallic GdNi adopts a CrB type of crystal structure (space group Cmcm), and it orders ferromagnetically via a second-order phase transition at 70 K, exhibiting unusually strong spontaneous striction along the three independent crystallographic axes in the ferromagnetically ordered state. Here we introduce a microscopic model to describe anisotropic changes of lattice parameters and elastic contribution to magnetocaloric effect of GdNi. In the model, results of density functional theory (DFT) calculations are used as inputs into a Hamiltonian that includes elastic energy of an anisotropic crystal lattice, exchange interactions, and Zeeman effect. The magnetic and elastic Hamiltonians are coupled through an anisotropic Bean-Rodbell model of magnetoelastic interactions. This coupling gives rise to anisotropic changes in the lattice parameters observed experimentally, and the model reveals good to reasonable agreements between the current theoretical results and earlier experimental data, thus validating the model within the limits of assumptions made. We also show that DFT calculations with 4f electrons of Gd treated as core electrons lead to a more adequate estimate of elastic constants of GdNi in comparison with the LDA + U method where 4f electrons are treated as valence electrons.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Electronic, magnetic, and structural properties of V2CoAl: Experimental and computational study

Here, we present results of combined experimental and computations study of V2CoAl, a Heusler alloy that exhibits nearly perfect spin-polarization. Our calculations indicate that this material maintains a high degree of spin-polarization (over 90%) in the wide range of lattice parameters, except at the largest considered unit cell volume. The magnetic alignment of V2CoAl is ferrimagnetic, due to the antialignment of the magnetic moments of vanadium atoms in their two sublattices. The calculated total magnetic moment per formula unit is nearly integer at the optimal lattice parameter and at the smaller volumes of the unit cell, but it deviated from the integer values as the unit cell expands. This is consistent with the calculated variation in the degree of spin polarization with lattice constant. The expected ferrimagnetic behavior has been observed in the arc-melted V2CoAl sample, with a Curie temperature of about 80 K. However, the saturation magnetization is significantly smaller than the theoretical prediction of ∼2 μB/f.u., most likely due to the observed B2-type atomic disorder. The samples exhibit metallic electron transport across the measurement range of 2 K to 300 K.

Kharel, Parashu (ORCID:0000000171330718)↗
DOE OSTI2023

Microstructure Evolution of a Multimodal Gamma-Prime Ni-Based Superalloy Characterized by In Situ Diffraction

The relationship between the evolution of microstructure, deformation micromechanisms and mechanical properties is difficult to establish in multimodal size distribution $_γ$$'$ superalloys, as the microstructure evolves with both temperature and time, and multiple strengthening mechanisms across each size distribution contribute to mechanical performance. In situ X-ray scattering can offer unparalleled insight regarding microstructure evolution at the temperatures and stresses of importance to gas-turbine applications; however, in situ X-ray diffraction has not been applied to the study of multimodal $_γ$$'$ distribution superalloys. Herein, lattice parameter evolution of secondary and tertiary $_γ$$'$ precipitates in a representative superalloy, Nimonic 115, is determined between 750 °C and 950 °C and correlated to room-temperature SEM and microhardness values. A large positive lattice parameter misfit of secondary $_γ$$'$ induces precipitate splitting, and the tertiary $_γ$$'$ goes into dissolution at ~ 800 °C, but with little apparent change in hardness values. The volume fraction of $_γ$$'$ decreases above 900 °C and precipitate-matrix coherency is lost, and there is a corresponding decrease in microhardness values. Importantly, the diffraction analysis demonstrates the capability to determine critical microstructural parameters of both precipitate size distributions in situ, representing an additional tool for determining microstructure-mechanical property relationships of multimodal superalloys.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Dimensional interpolation for metallic hydrogen

In this work, we employ a simple and mostly accurate dimensional interpolation formula using dimensional limits D = 1 and D = ∞ to obtain D = 3 ground-state energy of metallic hydrogen. We also present results describing the phase transitions for different symmetries of three-dimensional structure lattices. The interpolation formula not only predicts fairly accurate energies but also predicts a correct functional form of the energy as a function of the lattice parameters. That allows us to calculate different physical quantities such as the bulk modulus, Debye temperature, and critical transition temperature, from the gradient and the curvature of the energy curve as a function of the lattice parameters. These theoretical calculations suggest that metallic hydrogen is a likely candidate for high temperature superconductivity. The dimensional interpolation formula is robust and might be useful to obtain the energies of complex many-body systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Ab Initio Modeling of fcc Fe-Co-Cr-Ni High Entropy Alloys with Full Composition Range

The Fe-Co-Cr-Ni quaternary system has been studied extensively in the past decade, not only because of the superior properties achieved like high tensile ductility and fracture toughness, but also it is the foundation for the development of FeCrCoNi-based HEAs. However, most of the investigations are mainly focusing on the equiatomic and semi-equiatomic compositions. The physical properties of non-equiatomic compositions are barely explored. In the current work, the ab initio approach is adopted to predict the lattice parameter, structure stabilities, elastic properties, and enthalpy of formations of fcc Fe-Cr-Co-Ni HEA single crystals with the special quasirandom structure (SQS) method. To expand the design of Fe-Co-Cr-Ni HEAs into a full composition range, the current simulations cover all the binaries, ternaries, and the whole quaternary system. The 2-D composition-property contour diagrams are created to show the physical properties in the ternary and quaternary systems. Furthermore, our investigation shows that the fcc alloys' lattice parameter increases with the addition of Fe and Cr and decreases with Ni and Co. In addition to the enthalpy of formation at o K, the shape distortion rate is proposed to be another essential parameter to evaluate crystal stability. The results show the addition of Cr would destabilize the fcc lattice and cause symmetry breaking. Finally, the result of Pugh’s ratio shows that most of the fcc alloys show ductile behavior (P > 1.75), especially for the alloys around Fe 3 Ni, FeCo, and Fe 2 NiCo (P > 2.5). The brittle behavior (P < 1.75) is located around Fe 3 Cr and Fe 2 CoCr. Meanwhile, Cr 2 NiCo and Cr 2 FeNiCo are considered promising compositions to be tried and verified experimentally because of the higher bulk modulus and moderate shear modulus.

36 MATERIALS SCIENCE↗
DOE OSTI2022

ORNL_AISD_NiNb

This dataset describes the nickel-niobium solid solution binary alloy, where the two constituent elements nickel (Ni) and niobium (Nb) are randomly placed on an underlying crystal lattice. This dataset for nickel-niobium (Ni-Nb) alloys available includes the formation energy and bulk modulus for each crystal structure. Each atomic sample has a disordered phase which is obtained starting from an initial regular crystal structure of type body-centered cubic (BCC), face-centered cubic (FCC), or hexagonal compact packed (HCP). The geometry optimization ensures that all the alloy samples reached the equilibrium with negative formation energy. We perform geometry optimizations using the LAMMPS simulation package [1], a flexible simulation tool for particle-based materials modeling at the atomic, meso, and continuum scales. We utilized the embedded atom model (EAM) potential for Ni and Nb developed in a previous study [2]. The potential could describe behaviors of the liquid and solid phases of Ni-Nb alloy. The structural factors and angular distributions of three atoms are well-matched with X-ray and ab initio-based molecular dynamics data. We prepared the three different crystals with different initial lattice parameters (3.52 Ã… for FCC, 3.32 Ã… for BCC, and 3.5 Ã… for HCP). We performed energy minimization in two steps. Firstly, we minimized the structures with an isotropic unit cell to minimize the side effects from our arbitrary lattice parameters for all other compositions. Then, we applied geometry optimization with a triclinic (non-orthogonal) unit cell to fully minimize the stress components to calculate the elastic constants. In this procedure, we chose 10,000 as the maximum number of allowable steps aimed at obtaining fully relaxed atomic geometries. The dataset consists of three sets of crystal structures. The first set contains 46,086 irregular crystal structures, each of them with 54 atoms, obtained through optimization starting from a regular BCC crystal structure. The second set contains 24,543 irregular crystal structures, each of them with 32 atoms, obtained through optimization starting from a regular FCC crystal structure. The third set contains 39,303 irregular crystal structures, each of them with 48 atoms, obtained through optimization starting from a regular HCP crystal structure. The atomic configurations within each set span the possible compositional range. The three sets have been unified in a global dataset, which is extremely heterogeneous in terms of crystal structures, lattice volumes, and atomic configurations. Organization of files inside the dataset: the dataset contains three subdirectories called • BCC_opt • FCC_opt • HCP_opt based on the type of initial regular structure used to start the geometry optimization. Inside each of these folders, every atomic structure is identified by a string “A_B_Câ€, where A denotes the number of Nb in the system, B denotes index of structure with a given Nb number, and C denotes the total number of structures generated with a given Nb number. For each optimized crystal structure identified by the unique string of characters “A_B_Câ€, three files are provided: • A_B_C_opt.xyz: The optimized geometries in xyz format • A_B_C_opt.cfg: The optimized geometries in cfg format. It includes cell information and atomic energy, and forces calculated from LAMMPS. • A_B_C.elastic: Raw data of 21 elastic constants from LAMMPS output. • A_B_C.bulk: Calculated upper and lower bounds of bulk modulus and averaged one based on Voigt-Reuss-Hill approach from *.elastic. References: [1] A. P. Thompson, H. M. Aktulga, R. Berger, D. S. Bolintineanu, W. M. Brown, P. S. Crozier, P. J. in 't Veld, A. Kohlmeyer, S. G. Moore, T. D. Nguyen, R. Shan, M. J. Stevens, J. Tranchida, C. Trott, and S. J. Plimpton. LAMMPS - a flexible simulation tool for particle-based materials modeling at the atomic, meso, and continuum scales. Comp. Phys. Comm., 271:108171, 2022. [2] Y Zhang, R Ashcraft, MI Mendelev, CZ Wang, and KF Kelton. Experimental and molecular dynamics simulation study of structure of liquid and amorphous ni62nb38 alloy. The Journal of chemical physics, 145(20):204505, 2016.

36 MATERIALS SCIENCE↗